1. Field of the Invention
This disclosure generally relates to methods and apparatus for coupling components to a circuit board.
2. Background Information
Conventionally, an electrical device (e.g., a processor) is mounted in a socket on a printed circuit board that includes a plurality of integrated circuits secured thereto. Heat dissipation may affect the operation of the processor and thus it is desirable to have a highly effective heat sink for the processor to remove heat generated by the processor. Heat sinks are often attached to the processors/circuit boards by way of thermally conductive epoxy/tapes, a spring-based metal clip, plastic devices, or spring/screw combinations.
The use of thermally conductive epoxy to mount a heat sink onto the surface of a printed circuit board may be a significantly complex manufacturing procedure thereby increasing the overall cost and complexity of manufacturing. For example, there may be a considerable level of difficulty to depositing an epoxy layer of uniform thickness between the circuit board and the heat sink. The heat sink and the circuit board must be pressed together with a certain amount of pressure for a certain amount of time and in a certain orientation. Failure to control these variables (pressure, time, and orientation) carefully may prevent proper operation of the heat sink. Furthermore, an effective technique to easily separate the heat sink from the processor once the interface has been heated is not known to exist.
As an alternative to epoxy, a spring-based metal clip can be used to retain the heat sink on the circuit board by snapping onto a BGA socket or edge of an ASIC interposer. Such a clip, however, creates a significant drawback. Specifically, the bowed configuration of the spring-based clip causes a large portion of the clip to protrude above the top surface of the heat sink taking away valuable fin surface area. Furthermore, in high power processor applications, the heat sink required for a given processor may have a much larger footprint than the processor itself. This need for such large heat sinks makes the use of wire clips incapable of supporting these heavy objects and puts high stresses on soldered joints.
A third mechanism for attaching heat sinks to processors/circuit boards includes using plastic components to hold the heat sink in place for thermal compression and structural constraint. Although plastics are beneficial due to their electrical insulation, they are inadequate for sustaining the forces and high temperatures associated with heat sinks used on high powered processors due to inevitable creep, reducing their effectiveness and potential catastrophic failure.
Finally there is a majority of systems designed that incorporate screws and springs combined with standoffs and/or brace structures to mount the heat sinks to the system. Apart from providing a structurally sound solution this design path is disastrous due volume of loose parts to track, assemble and properly tighten. One of the most significant drawbacks is the fact that a tool is required to perform installation or service.
With some heat sinks, the processor is installed into a socket on the circuit board and retained in place by a locking mechanism that may be integral to the socket. Processors may be installed onto a socket by hand and it is up to the installer to ensure proper alignment of the processor pins with the holes on the socket. Once the processor is installed, the heat sink is then affixed to the top of the processor by a thermally conductive interface. The size of the heat sink may be large enough to prevent unlocking and removing of the processor while the heat sink is installed. In these situations, the heat sink must be removed from the processor before the processor can be removed from the socket.
Therefore, there remains a need in the art for methods and apparatus that allow for heat sinks to be installed and uninstalled from a processor or other electrical device without the need for special rework instructions or tools, and performed in an intuitive, user friendly, easy manner. If a large heat sink is intended to be used and that heat sink size in turn requires a large force to hold it in place for shipping, there remains a need for a lever to provide mechanical advantage to apply that load. Furthermore, due to the large number of tolerance variations in PCBs, soldered joints, ASIC package heights, etc. there remains a need for a device that can be compliant and accept these variations while still providing equal load distribution.